1. Field of the Invention
The present invention relates to apparatus used for the repairing, reworking and/or production of electronic components and circuit boards and which use a flow of hot air to re-melt solder retaining the electronic components on a substrate, such as a circuit board. More specifically, the present invention relates to such apparatus which have a vacuum pickup device for placing and/or removing components on/from the substrate once the solder has been caused to flow.
2. Description of Related Art
In apparatus for the removal and installation of electronic components with respect to substrates, such as printed circuit boards, it is know to provide a vacuum pick-up device for placing and/or removing components on/from the substrate once the solder has been caused to flow. For example, U.S. Pat. Nos. 4,899,920 and 4,972,990 show stationary apparatus in which a vacuum tube with a suction cup on its end extends through the heating head. The vacuum tube is connected to a vacuum source and is axially displaceable within the heater head so as to be movable through the heater nozzle into contact with the component to be lifted off of a circuit board and then to remove it once the solder has melted, or to hold and place a component onto the circuit board. Movement of the pickup tube is produced solely via a manually turnable knob on the heater head.
Thus, this device depends on the touch sensitivity of the use to prevent pickup tube from pressing down too hard on the component during placement of the component or during attachment of the pickup to a mounted component. Likewise, for dismounting of a component, care must be taken to prevent lifting of the tube too early or too late, resulting in either detachment of the pickup device from the component or damage to the component due to insufficient melting of the solder in the former case or re-solidification of the solder in the latter case.
In another known system (JBC Model JT 6040), a combined pickup device and component shield well structure is used with a separate, handheld blower. The well is a tubular wall structure that is placed around a component to be removed from a substrate, and from which rise a stanchion which holds a vacuum pickup tube. The vacuum pickup tube is held in a raised position by a coil spring. In use, with the vacuum turned on, the pickup tube is manually lowered against the action of the spring until contact is made with the component, at which point the vacuum holds the pickup tube to the component and the pickup tube can then be released. The outlet end of the hot air blower is then directed into the shield well and hot air is blown against the solder connections to melt them. As soon as the solder connections have sufficiently melted to release the component leads, the spring force acting on the pickup tube causes it to lift, thereby removing the component from the substrate.
Such a device is advantageous since it ensures that component is lifted at the proper time. However, such a device is effective only for dismounting of components since the one-way spring action is counterproductive in those cases where a component is to be mounted. Furthermore, the need for separate dismounting and heating devices is less convenient and more costly than a single apparatus which can serve both functions.
Devices are also known (OK Industries Model FCT2228 handle of the FCR2200 rework system) in which the vacuum pickup tube is acted on by a spring in direction toward the component so as to provide a resilient cushion against which the pickup tube can be displaced when contact is made with a component to prevent it from being inadvertently damaged by the application of too great a downward force. However, such devices can pose problems when mounting of a component by applying too great a force to the component so that, upon melting of the solder, the leads splash the solder and/or pass through it in a way that produces defective solder connections. Furthermore, such arrangements do not provide for the automatic removal of a component.
Thus, there is a need for a vacuum pickup device that can be incorporated into handheld and stationary soldering and desoldering devices, and which can be used so as to gently place components to be mounted as well as gently engage mounted components, and which also has the capacity to automatically lift components off of a substrate as soon as the solder connections have been re-melted.
It is also noted that, up to this time, the handpieces of soldering/desoldering apparatus have relied either footswitches or handswitches on a separate master control unit for turning on and off the vacuum supply and/or hot air supply, with most units currently available merely having a master on/off switch, so that the vacuum pump and hot air supply are constantly running the entire time that the unit is on.
Thus, it is desirable to provide a more user friendly control arrangement for handpieces of soldering/desoldering apparatus. In particular, there is a need for such a control which provides independent cycling on and off of the hot air and vacuum supplies and does so on the handpiece in a way which will avoid problems of components being inadvertently dropped due to accidental actuation of the vacuum on-off switch.